The present invention generally relates to apparatus and methods for providing clean core air in an engine and, more specifically, to apparatus and methods for separating particles from diffuser air.
Corrosive dust and salt particle deposits may be responsible for hot corrosion in the turbine and blockage of air-cooling passages (effusion cooling holes) in the combustion liner and internal cooling passages in turbine airfoils. Removal of dust from the core airflow is required to significantly improve turbine and combustor durability.
For example, as turbine inlet temperatures continue to increase to improve the efficiency of modern gas turbine engines, a large number of small cooling holes are required along combustor liners and turbine airfoils to cool the components. These small cooling holes can plug with dust particles, reducing the effectiveness of the cooling and causing oxidation and thermal-mechanical fatigue. Distress may also be observed on high performance turbine stator and blade leading edges and airfoil pressure side surfaces due to glass deposits on the thermal barrier coating (TBC). The dust particles may melt and wick into the TBC, reducing the compliance of the TBC micro-structure. The result may be spallation of the TBC coating which may elevate the airfoil metal temperatures and cause oxidation and thermal-mechanical fatigue distress.
U.S. Pat. No. 4,463,552, issued to Monhardt et al., discloses that a surge valve in the compressor may be used to remove dirt from the air flowpath. The surge valve is placed between the low and high pressure compressor, diverting dust into the bypass air. The '552 patent, however, does not disclose apparatus or methods for removing particles from an air flow within the diffuser or at the exit of the diffuser.
U.S. Pat. No. 3,338,049, issued to Fernberger, describes a particle separator in front of the inlet to the compressor. This separator has an inflatable inner wall to alter air flow and divert particles into a bypass duct. The '049 patent, however, does not disclose apparatus or methods for removing particles from an air flow within or at the exit of the diffuser.
As can be seen, there is a need for improved methods and apparatus to improve the air quality in the core of gas turbine engines for improved durability.